The present invention relates to a fuel cell system with a cooling device.
Fuel cells are planned to be used increasingly in both stationary and mobile applications. In mobile or vehicle applications, fuel cells can be used as a vehicle drive mechanism or as a so-called auxiliary power unit (APU).
In the operation of the fuel cells or the fuel cell stack, besides electrical energy, thermal energy is generated as well. The thermal energy is often dissipated as waste heat with the aid of cooling or a coolant loop. The waste heat is sometimes used for heating applications.
The cooling of the fuel cell or fuel cell stack includes a coolant loop, for instance, which is driven by means of a pump. The coolant loop further includes a heat exchanger, which in turn has air blown at it with the aid of a blower or fan, so that heat is dissipated to the ambient air.
From German Patent Disclosure DE 195 17 813, a method for regulating the heat-guided operation of fuel cell systems is known that regulates the forward-flow or return-flow temperature of the coolant or effective-heat loop by means of an adaptation to the heat demand of the consumer. The forward-flow or return-flow temperature of the coolant or effective-heat loop is regulated such that a temperature that is as close as possible to just below the allowable maximum value is set. As a result, a continuous adaptation of the heat production by the fuel cell to the current heat demand is achieved.
From German Patent DE 198 25 286 C2, a fuel cell system with a coolant loop as sketched above is known, in which the temperature distribution in the fuel cell is detected, by way of measuring the forward-flow or return-flow temperature of the coolant and the resultant difference, or by means of measuring the internal temperature. The coolant throughput through the fuel cell is controlled in agreement with the parameters, reflecting the temperature distribution inside the fuel cell, using a preset value corresponding to a nonuniform temperature.